Siemens siprotec 7SD5 User Manual page 41

The Direct Local Trip (address 122 DTT Direct Trip) is a command that is initiated
from an external device for tripping the local circuit breaker.
With address 125 Weak Infeed you can select a supplement to the teleprotection
schemes. Set Enabled to apply the classical scheme for echo and weak infeed trip-
ping. The setting Logic no. 2 switches this function to the French specification. This
setting is available in the device variants for the region France (only version 7SD5***-
**D** or 10th digit of order number = D).
At address 126 Back-Up O/C you can set the characteristic group which the time
overcurrent protection uses for operation. In addition to the definite time overcurrent
protection, an inverse time overcurrent protection may be configured depending on
the ordered version. The latter operates either according to an IEC characteristic (TOC
IEC) or an ANSI characteristic (TOC ANSI). For the characteristics please refer to the
Technical Data. You can also disable the time overcurrent protection (Disabled).
At address 131 Earth Fault O/C you can set the characteristic group which the
earth fault protection uses for operation. In addition to the definite time overcurrent
protection, which covers up to three phases, an inverse-time earth fault protection
function may be configured depending on the ordered version. The latter operates
either according to an IEC characteristic (TOC IEC) or an ANSI characteristic (TOC
ANSI) or according to a logarithmic-inverse characteristic (TOC Logarithm.). If an
inverse-time characteristic is not required, the stage usually designated „inverse time"
can be used as the fourth definite-time stage (Definite Time). Alternatively, you
can select an earth fault protection with inverse-time characteristic U0 inverse or a
zero sequence power protection Sr inverse. For the characteristics please refer to
the Technical Data. You can also disable the earth fault protection (Disabled).
When using the earth fault protection, it can be complemented by teleprotection
schemes. Select the desired scheme at address 132 Teleprot. E/F. You can
select the direction comparison scheme Dir.Comp.Pickup, the unblocking scheme
UNBLOCKING and the blocking scheme BLOCKING. The procedures are described in
detail in Section 2.9. If you do not want to use teleprotection in conjunction with earth
fault protection set Disabled.
If the device features an automatic reclosing function, address 133 and 134 are of im-
portance. Automatic reclosure is only allowed in overhead lines. It should not be used
in any other case. If the protected object consists of a mixture of overhead lines and
other equipment (e.g. overhead line in block with a transformer or overhead line/ca-
ble), it must be ensured that reclosure can only be performed in the event of a fault on
the overhead line. If no automatic reclosing function is desired for the feeder at which
7SD5 operates, or if an external device is used for reclosure, set address 133 Auto
Reclose to Disabled.
Otherwise set the number of desired reclosing attempts there. You can select 1 AR-
cycle to 8 AR-cycles. You can also set ADT (adaptive dead times). In this case the
behaviour of the automatic reclosing function is determined by the cycles of the
remote end. The number of cycles must however be configured at least in one of the
line ends which must have a reliable infeed. The other end — or other ends, if there
are more than two line ends — may operate with adaptive dead time. Section 2.15 pro-
vides detailed information on this topic.
The AR control mode at address134 allows a maximum of four options. Firstly, it
can be determined whether the auto-reclose cycles are carried out according to the
fault type detected by pickup of the starting protective function(s) (only three-pole trip-
ping), or according to the type of trip command. Secondly, the automatic reclosing
function can be operated with or without action time.
The setting Trip with T-action / Trip without T-action ... (default
setting = Trip with T-action ...) is preferred if single-pole or single-pole/three-pole auto-
7SD5 Manual
C53000-G1176-C169-1
2.1 General
41